1. Field of the Invention
The present invention relates to an etching method, and particularly relates to a dry etching method. Priority is claimed on Japanese Patent Application No. 2004-5219 filed on Jan. 13, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, the dry etching method has been widely used for etching an etching object arranged on a surface of a substrate (see Japanese Unexamined Patent Application, First Publication Nos. 2001-284307 and 2003-124172).
For example, when an etching object formed of a silicon oxide film formed on a surface of a silicon substrate is etched, there is a method in which the substrate is first arranged in a processing chamber, and after a vacuum atmosphere is formed in the processing chamber, an intermediate product reacting with the etching object is produced in the processing chamber. For example, when free radicals of a hydrogen gas and an etching gas such as a fluoride gas are supplied to the processing chamber, the etching gas is reduced, to produce an intermediate product such as NHxFy (x and y are optional integers).
The intermediate product reacts with the etching object on the surface of the substrate, to produce a reaction product. When the substrate is heated, the reaction product is thermally decomposed to become a pyrolysis gas and is evaporated, and as a result, the etching object is removed from the surface of the substrate.
Thus, according to the dry etching method, the silicon oxide film can be removed by etching in the vacuum atmosphere, and hence the silicon substrate is not contaminated by moisture and oxygen in the air.
According to the conventional dry etching method, however, the in-plane distribution of the etching quantity with respect to the surface of the substrate becomes nonuniform. Particularly, when a plurality of substrates is etched simultaneously, the in-plane distribution of the etching amount and the etching rate becomes different for each substrate.